This invention relates in general to methods and apparatus for the video inspection of articles of manufacture. More specifically, this invention relates to video inspection systems and methods wherein an article of manufacture is observed by a video camera as it passes through an illuminated inspection station. Such a system is disclosed in U.S. Pat. No. 4,002,823 issued to Van Oosterhout which teaches a video inspection system for glassware.
In the Van Oosterhout type system, generaly known as a bright field analyzer in the electronic video inspection art, semi-diffused light is directed through a glass bottle to be inspected and is observed by a video camera. The camera produces for each of its scan lines a video signal indicative of the spatial rate of change of the optical refraction characteristic of the scanned portion of the article. Signal processing circuits distinguish between desired refraction characteristics of the article, such as, those produced by lettering, seams, and coloration and undesired refraction characteristics such as those produced by spikes, bird swings and other defects.
Even though the inspection system taught by Van Oosterhout has greatly enhanced the art of bottle inspection, its capabilities are nevertheless limited.
One particular limitation of the Van Oosterhout system is that decorative bottle features often produce, through the signal processing circuits signals, indicia of undesired refraction characteristics causing, rejection of a bottle having no defects. Bright field analyzer video inspection systems utilize an inspection window which defines a region of each bottle to be inspected. Preset inspection criteria are applied throughout this entire region. Therefore, decorative bottle portions within the inspection window may cause an inappropriate rejection. There is no way to inhibit the inspection of smaller regions within the inspection window corresponding to decorative bottle portions.
Another problem involves the scanning of the shoulder region of a bottle. As a video camera scans a bottle under inspection, the scan line crosses the leading edge of the bottle first, it then crosses the body of the bottle, and finally crosses the trailing edge of the bottle. On the shoulder of a bottle, the bottle's leading and trailing edges are particularly thick and tend to "fool" the signal processing circuits into thinking that a defect has been detected. In order to prevent such false defect indications, edge removing circuits, generally referred to as shoulder blanking circuits, are provided to inhibit defect signals generated in response to the scan crossing the leading and trailing edges of the shoulder of a bottle. In essence, shoulder blanking is achieved by generating a horizontal line bar to cover the neck of a bottle. In the case where the entire shoulder of the bottle to be blanked is located within the inspection window, rejection due to apparent defects are inhibited within the shoulder region. However, in the case where the entire container is not viewed by the video camera, it is impossible to provide a continuous shoulder blanking signal. Therefore, the size of the bottle capable of being inspected is limited.
In addition, the bright field analyzer video inspection system in current use does not provide for the automatic counting of the total number of bottles inspected, nor does it provide for the automatic counting of the total number of bottles rejected upon inspection.